1. Field of the Invention
The present invention relates to a recording medium cartridge such as a recording tape cartridge or the like which accommodates a single reel within a case and a recording tape such as a magnetic tape or the like which is principally employed as a recording/replaying medium of a computer or the like being wound onto the reel, and to a recording tape cartridge fabrication method.
2. Description of the Related Art
Heretofore, a recording tape cartridge has been known in which a recording tape such as a magnetic tape or the like is wound onto a single reel and the reel is rotatably accommodated in a case made of synthetic resin, and the recording tape cartridge is employed as a data recording/replaying medium of a computer or the like (for data backups). Such a recording tape cartridge commonly has a structure in which braking of the reel at a time of non-use (when the cartridge is not loaded in a drive device) is mechanically implemented only for a rotation direction, while the reel is urged in a rotation axis direction by urging means such as a coil spring or the like.
However, with such a structure, if an impact acts on the recording tape cartridge at a time of non-use, due to mishandling by a user or a droppage or the like, it is easy for the reel to move in the rotation axis direction because of this impact and, in some cases, the rotation direction braking of the reel may be released and creases or the like may be formed in the recording tape. Therefore, in recent years, as illustrated in, for example, Japanese Patent Application Laid Open (JP-A) No. 2005-276416, recording tape cartridges have been proposed which are structured such that, at a time of non-use, the reel is restricted so as not to move in the rotation axis direction, and that restriction is easily released for a time of use.
The recording tape cartridge mentioned above has a structure in which, at a time of non-use, a lock member is inserted in between an upper flange of the reel and a ceiling plate of the case, and thus the reel is restricted so as not to move in the rotation axis direction. That is, the structure is such that, because of the lock member, there is no space for the reel to move in the rotation axis direction. With this structure, at a time of use, a releasing operation is employed in which a brake member which restricts the reel in the rotation direction is raised by a release member of a drive device and the lock member slides in a radial direction of the reel and is withdrawn (i.e., the restriction by the lock member is released).
Accordingly, because the lock member slides against the brake member which restricts the reel in the rotation direction and against the ceiling plate of the case, coefficients of dynamic friction with these members are important. If, for example, polycarbonate (PC) is chosen for the case and polyamide (PA) is chosen for the lock member, in tests by the present applicant, a dynamic friction coefficient of PA against PC is 0.1. With a lock member in which 20% polytetrafluoroethylene (PTFE) is added to polyacetal (POM) to improve sliding, the dynamic friction coefficient is 0.09, and thus sliding characteristics of the PA can be said to be excellent.
However, in actual usage, it has become clear in recent years that it is not sufficient only to consider sliding characteristics of the synthetic resin materials. Specifically, when a recording tape cartridge is loaded into a drive device and the release member of the drive device begins the operation for releasing the brake member, if, for example, the brake member employs PA, a peak in a load which is applied for raising the brake member is, as shown in FIG. 10, of the order of about 10 N (Newtons) after 0.1 seconds (as shown by the broken line α).
However, during transport, during loading into a library device and suchlike, acceleration impacts of around 30 G (G being the acceleration of gravity) are applied to the recording tape cartridge, and with a recording tape cartridge to which such acceleration impacts have been applied, for example, about 20,000 times, a proportional increase in the above-mentioned load is as much as about 40% (becoming about 14 N, as shown by the solid line β). Thus, even when the dynamic friction coefficient is low and sliding characteristics are excellent, in an environment in which acceleration impacts are successively applied, the excellence or non-excellence of sliding characteristics cannot be determined just by the dynamic friction coefficients of the synthetic resin materials.
A coefficient of dynamic friction is measured by performing tests of sliding materials against each other while applying certain loads. However, if an acceleration impact is applied when performing tests are conducted, then if the brake member employs, for example, PA, an impact exceeding 50 G is momentarily applied. With such a load, the lock member acts to move slightly while touching against the case, and a phenomenon similar to the stick-slip phenomenon may occur. This phenomenon is thought to be caused by the PA and PC slightly gouging into one another and producing powder, and this powder then being crushed by the PA.
That is, each time an operation for loading the recording tape cartridge into the drive device or an operation for loading into a library device or the like is repeated, the lock member slides a little in a state in which a pressure of 30 G or more is acting between the lock member and the brake member and/or ceiling member. Thus, the lock member is abraded and powder is produced. Hence, because of this powder, an “adhering phenomenon” occurs, sliding resistance of the lock member increases, and a release force for releasing the reel from the state of times of non-use (a “brake release force”) becomes larger. When this problem arises, it may lead to damage to the lock member, a breakdown of the drive device, or the like.